The dopamine transporter (DAT) has been identified as the principal brain receptor site best correlated with the rewarding and euphoric properties of cocaine. Cellular and subcellular localization data are important to help to elucidate the functional properties of this important brain molecule. In previous FYs, investigators in this Branch described the detailed distributions of the dopamine transporter mRNA in cells of the rat and human brains. In this FY, studies of the distribution of the DAT protein in rat brain were substantially advanced. Light-microscopy revealed details of the distribution of DAT distribution in rat brain that included remarkably dense fiber distributions in specific laminae of the frontal cerebral cortex. Ultrastructural studies of the transporter revealed that most of the DAT immunoreactivity was found in intracellular and plasma membrane localizations not readily associated with conventional synaptic specializations. These studies substantially add to information on the detailed cellular localizations of these important sites for cocaine reward, and underscore the possibility that extrasynaptic removal of dopamine provides a principal function of the DAT.